improve readme

Author: zilongshanren

README.md

@@ -15,7 +15,7 @@ As an example, if you want to support cocos2d-x in ARM64, you need to compile al
 
 - We use Ubuntu to build all the static libraries for Linux.
 
-- Other platforms is not tested which means if you use windows to build static libraries for Android, it might be failed.
+- Other platforms is not tested which means if you use Windows or Linux to build static libraries for Android, it might be failed.
 
 
 ## Download
@@ -38,9 +38,9 @@ brew install m4
 - If you want to build static libraries for iOS and Mac, you should install the latest version of XCode.  You should also install the `Command Line Tools` bundled with XCode.
 
 
-- If you want to build static libraries for Android, you should install [NDK](https://developer.android.com/tools/sdk/ndk/index.html). NDK r9d is required at the moment and you should also specify the ANDROID_NDK environment variable in your bash configure file.
+- If you want to build static libraries for Android, you should install [NDK](https://developer.android.com/tools/sdk/ndk/index.html). NDK r9d is required at the moment and you should also specify the ANDROID_NDK environment variable in your shell.
 
-- If you want to build static libraries for Tizen, you should download and install [Tizen SDK](https://developer.tizen.org/downloads/tizen-sdk). And you should also add a environment variable named `TIZEN_SDK` in your bash configure file.
+- If you want to build static libraries for Tizen, you should download and install [Tizen SDK](https://developer.tizen.org/downloads/tizen-sdk). And you should also add a environment variable named `TIZEN_SDK` in your shell.
 
 ### For Linux users
 xxx need to improve the document here later.
@@ -85,6 +85,7 @@ OPTIONS
 If you want to build *websockets* with *i386* arch, you could use the following command:
 
 ```cpp
+cd build/ios
 ./build.sh -s -a i386 -l websockets (Don't forget the -s option, it is stand for simulator, if you omit it, it will give you errors.)
 ```
 
@@ -125,6 +126,7 @@ EOF
 If you want to build a `curl` library with `armeabi` arch support, you can do it like this:
 
 ```cpp
+cd build/android
 ./build.sh -a armeabi -l curl
 ```
 
@@ -136,8 +138,15 @@ cd build/mac
 ./build_png.sh
 ```
 ### For Tizen
+For building libpng armv7 arch library:
+
+```cpp
+cd build/tizen
+./build_png.sh
+```
 
 ### For Linux
+xxx After testing these scripts on Linux, document will be update.
 
 ## How to build a DEBUG and RELEASE version
 xxx we need to improve the script to add debug and release options.